FIGS. 1A and 1B depict the structure of a capacitance type touch panel which is described in Japanese Patent Application Laid Open No. 2010-218542 (hereinafter referred to as “Patent Literature 1”) as an existing example of a touch panel.
On a front surface 11a of a substrate 11, detection electrodes 12 and wiring electrodes 13 electrically connected to the detection electrodes 12 are formed. The wiring electrodes 13 transmit a detected signal to an external circuit. The detection electrodes 12 are formed on a part of the substrate 11 excepting the marginal region thereof to define a detection region 14, and the wiring electrodes 13 are collectively formed outside the detection region 14 to define a wiring region 15. Outside a region including the detection region 14 and the wiring region 15, that is, in the outer periphery of the substrate 11, a first shielding electrode 16 is formed.
An insulating layer 17 is formed on the detection region 14, the wiring region 15 and the first shielding electrode 16. A second shielding electrode 18 is formed on a top surface of the insulating layer 17 so as to cover the wiring region 15 and the first shielding electrode 16. The second shielding electrode 18 is electrically connected to the first shielding electrode 16 via a through hole 19 formed in the insulating layer 17. The first shielding electrode 16 is connected to a GND not shown in the drawings.
The wiring electrodes 13 are collected at a right-hand side end of the substrate 11 to form a terminal portion (which is hidden in FIG. 1A), and one end of a first flexible substrate 21 is connected to the terminal portion. A signal processing IC 22 is mounted on the first flexible substrate 21. A second flexible substrate 23 is connected to the other end of the first flexible substrate 21. The second flexible substrate 23 is connected to a control unit not shown in the drawings.
The touch panel having the above-described structure blocks out the electromagnetic noise invading from an end of the substrate 11 (from a lateral direction of the substrate 11) by the first shielding electrode 16 before the electromagnetic noise reaches the wiring electrodes 13 and the detection electrodes 12 and further blocks out the electromagnetic noise invading from the top surface of the substrate 11 (from above) by the second shielding electrode 18.
As described above, Patent Literature 1 discloses that, by forming the first shielding electrode 16 and the second shielding electrode 18 in the touch panel, the electromagnetic noise invading from the top surface or the end of the substrate 11 is blocked out and further discloses that static electricity is also blocked out.
The insulating layer 17 interposed between the second shielding electrode 18, which is formed to cover the wiring electrodes 13, and the wiring electrodes 13 is thin. When the static electricity applied from the outside moves to a portion of the second shielding electrode 18, for example, the portion facing the wiring electrodes 13, the static electricity may move to the wiring electrodes 13 through a minute pinhole present in the insulating layer 17 or as a result of the occurrence of a dielectric breakdown in the insulating layer 17.
Such a movement of the static electricity to the wiring electrodes 13 becomes a cause of a malfunction. Additionally, if a current flowing in the wiring electrodes 13 due to the static electricity exceeds the allowable current of the wiring electrodes 13, the wiring electrodes 13 will fuse (will be broken down).